This invention relates in general to plasma generators, and more particularly to a radio frequency plasma generator capable of exciting electrons to a uniform energy level. The term "plasma" is intended herein to mean a neutral plasma, i.e., a collection of positive, negative and neutral particles having a total net charge substantially equal to zero.
There are numerous applications of plasma discharges, such as for plasma etching, sputtering, etching by chemically active discharges, generating excited and/or metastable states for lasers, generating black body (flash lamp) or fluorescent light, and various other applications. The generation of such plasmas may be accomplished in several ways, such as by the bombardment of a gas with high energy electrons, by the application of direct current or alternating current (radio frequency or microwave) electric fields to a gas, by the elevation of the temperature of a gas (by any means) to the region of thermal ionization, by the ionization of the gas by photons, and by subjecting the gas to radioactive materials.
In many applications, especially those for generating excited states for lasers, the desired or useful excitation process involves the transfer of a very precise amount of energy corresponding to the quantum level of the reaction. With the exception of narrow band photon sources, the energy sources presently available to drive the lasing process have a broad random energy distribution, and only the energy within the narrow range which drives the desired process is of any use. Furthermore, the energy outside the useful range can cause undesirable reactions. Also, even though narrow band photon sources may drive a process at the proper energy level, such photon sources are either lasers or otherwise very power and efficiency limited, and are therefore not practical for high power applications.